Vertical batch furnace assembly

ABSTRACT

Vertical batch furnace assembly for processing wafers comprising a cassette handling space, a wafer handling space, and a first wall separating the cassette handling space from the wafer handling space. The first wall has at least one wafer transfer opening in front of which a wafer transfer position for a wafer cassette is provided. The cassette handling space comprises a cassette storage, and a cassette handling mechanism. The cassette storage has a plurality of cassette storage positions and is configured to store a plurality of wafer cassettes. The cassette handling mechanism comprises a first cassette handler which is configured to transfer wafer cassettes between a first set of the cassette storage positions and the wafer transfer position. The cassette handling mechanism is provided with a second cassette handler which is configured to transfer wafer cassettes between a second set of the cassette storage positions and the wafer transfer position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patent application Ser. No. 16/935,280 filed Jul. 22, 2020 titled VERTICAL BATCH FURNACE ASSEMBLY; which claims the benefit of U.S. Provisional Patent Application Ser. No. 62/880,890 filed Jul. 31, 2019 titled VERTICAL BATCH FURNACE ASSEMBLY, the disclosures of which are hereby incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a vertical batch furnace assembly for processing wafers.

BACKGROUND

Most vertical batch furnace assemblies are provided with a cassette handling space for receiving and storing wafer cassettes therein. Such a cassette handling space is typically provided with a cassette handling mechanism for transferring wafer cassettes between a cassette in-out port, a cassette storage and a wafer transfer position. At the cassette in-out port wafer cassettes may be exchanged between the vertical batch furnace assembly and the cleanroom-environment in which the vertical batch furnace assembly is accommodated. The received wafer cassettes may be placed in the wafer transfer position from which position wafers may be unloaded from the wafer cassette and loaded to a wafer boat for processing of said wafers.

The cassette storage may have a plurality of cassette storage positions on each of which a wafer cassette may be stored. The cassette storage positions may be arranged in a storage rack, provided with for example a storage carrousel. In order to be able to reach the in-out port, the wafer transfer position and all of the wafer storage positions, a typical cassette handling mechanism may comprise an elevator mechanism and a robot arm. The elevator mechanism may provide a vertical movement of the cassette handling mechanism in order to reach the cassette storage positions at different vertical heights. The robot arm may provide a two-dimensional horizontal movement in order to reach at least some of the storage positions.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form. These concepts are described in further detail in the detailed description of example embodiments of the disclosure below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

It is realized that typically a plurality of wafer cassettes may need to be unloaded to load an entire wafer boat. It is realized that it may be desirable to store as many wafer cassettes within the cassette handling space as possible. That the cassette handling space may have a rectangular-shaped footprint. That elaborate cassette handling mechanisms may be required to have sufficient reach in order to be able to reach cassette storage positions within a cassette handling space. That the speed with which the cassette handling mechanism can transfer the cassettes within the cassette handling space, may be important for the efficiency of the vertical batch furnace assembly.

Therefore, it may be an object to provide a vertical batch furnace assembly of which the cassette handling mechanism has an improved transfer speed and/or an improved reach.

To that end, there may be provided a vertical batch furnace assembly according to claim 1. More particularly, there may be provided a vertical batch furnace assembly for processing wafers. The vertical batch furnace assembly may comprise a cassette handling space, a wafer handling space, and a first wall separating the cassette handling space from the wafer handling space. The first wall may have at least one wafer transfer opening in front of which, at a side of the first wall which is directed to the cassette handling space, a wafer transfer position for a wafer cassette may be provided. The cassette handling space may comprise a cassette storage, and a cassette handling mechanism. The cassette storage may have a plurality of cassette storage positions and may be configured to store a plurality of wafer cassettes provided with a plurality of wafers. The cassette handling mechanism may comprise a first cassette handler configured to transfer wafer cassettes between a first set of the cassette storage positions and the wafer transfer position. The cassette handling mechanism may be provided with a second cassette handler configured to transfer wafer cassettes between a second set of the cassette storage positions and the wafer transfer position.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Various embodiments are claimed in the dependent claims, which will be further elucidated with reference to an example shown in the figures. The embodiments may be combined or may be applied separate from each other.

All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE FIGURES

While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the invention, the advantages of embodiments of the disclosure may be more readily ascertained from the description of certain examples of the embodiments of the disclosure when read in conjunction with the accompanying drawings, in which:

FIG. 1 shows a top, partially sectional view of an example of a vertical batch furnace assembly according to the description;

FIG. 2 shows a top, sectional view of the cassette handling space of the example of FIG. 1 ; and

FIG. 3 shows a side, sectional view of another example of the cassette handling space according to the description.

DETAILED DESCRIPTION OF THE FIGURES

In this application similar or corresponding features are denoted by similar or corresponding reference signs. The description of the various embodiments is not limited to the example shown in the figures and the reference numbers used in the detailed description and the claims are not intended to limit the description of the embodiments, but are included to elucidate the embodiments by referring to the example shown in the figures.

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below. The illustrations presented herein are not meant to be actual views of any particular material, structure, or device, but are merely idealized representations that are used to describe embodiments of the disclosure.

As used herein, the term “wafer” may refer to any underlying material or materials that may be used, or upon which, a device, a circuit, or a film may be formed.

In the most general term the present disclosure may provide a vertical batch furnace assembly 10 for processing wafers, as illustrated in FIG. 1 . The vertical batch furnace assembly 10 may comprise a cassette handling space 12 (illustrated in more detail in FIG. 2 ), a wafer handling space 14, and a first wall 16 separating the cassette handling space 12 from the wafer handling space 14. The first wall 16 may have at least one wafer transfer opening 18 in front of which, at a side of the first wall 16 which is directed to the cassette handling space 12, a wafer transfer position 20 for a wafer cassette 22 may be provided. The cassette handling space 12 may comprise a cassette storage, and a cassette handling mechanism 26, 28. The cassette storage may have a plurality of cassette storage positions 24 and may be configured to store a plurality of wafer cassettes 22 provided with a plurality of wafers. The cassette handling mechanism 26, 28 may comprise a first cassette handler 26 configured to transfer wafer cassettes 22 between a first set 30 of the cassette storage positions 24 and the wafer transfer position 20. The cassette handling mechanism 26, 28 may be provided with a second cassette handler 28 configured to transfer wafer cassettes between a second set 32 of the cassette storage positions 24 and the wafer transfer position 20.

An advantage of the above-mentioned vertical batch furnace assembly is that each cassette handler 26, 28 is able to reach at least a part of the cassette storage positions 24 within the cassette handling space. There is no single robot arm which needs to be able to reach every cassette storage position. It is sufficient have the first cassette handler 26 transfer to and from the first set 30 of cassette storage positions 24, and the second cassette handler 28 transfer to and from the second set 32 of cassette storage positions 24, as long as the first and second sets 30, 32 together include all cassette storage positions 24 of the cassette storage. By choosing the location of the first and the second cassette handler 26, 28 within the cassette handling space 12 carefully with respect to the cassette storage positions 24, each can have a limited reach while they together can still cover all cassette storage positions 24 within the entire cassette handling space 12. The first cassette handler 26 may e.g. be arranged at or near a first end of the cassette handling space 12, while the second cassette handler 28 may be arranged at or near a second end of the cassette handling space 12, opposite the first end. The first set 30 of cassette storage positions 24 will then cover roughly half of the cassette handling space 12 near the first end, while the second set 32 of cassette storage positions 24 will cover roughly another half the cassette handling space 12 near the second end. Because both the first cassette handler 26 and the second cassette handler 28 only need to cover roughly half of the area with respect to a known cassette handler, the reach may be much smaller. A smaller reach means that a less elaborate and thus a more inexpensive cassette handler may be used.

Secondly, by having two cassette handlers 26, 28 both cassette handlers 26, 28 may transfer a wafer cassette towards the wafer transfer position. They may do so simultaneously. This means that while the first cassette handler 26 is placing a wafer cassette 22 in the wafer transfer position 20, the second wafer handler 28 may already be getting another wafer cassette 22 from a cassette storage position 24 of the cassette storage. By cleverly choosing where to store a wafer cassette 22 and choosing the order in which the wafer cassettes 22 are transferred from the cassette storage to the wafer transfer position 20, a high overall transfer capacity of the cassette handling mechanism 26, 28 may be reached. With such a scheme the total transfer capacity of the cassette handling mechanism may simply be the sum of transfer capacities of the first and the second cassette handler 26, 28. To improve the total transfer capacity of the cassette handling mechanism 26, 28, the transfer speed of both the first and second cassette handers 26, 28 only needs to be more than half the transfer speed of a prior art cassette hander. A smaller transfer speed means that a less robust and thus an even more inexpensive cassette handler may be used. Because of the lower transfer speed, the wafer cassette 22 may also be transferred more smoothly, reducing the risk of particle release which could damage wafers.

By using the first and the second cassette handlers 26, 28, both the reach may be improved and the transfer capacity may be increased relative to prior art cassette handler mechanism of vertical batch furnaces.

In an embodiment, the first and the second cassette handler 26, 28 may be each provided with a cassette handler arm 34, and an elevator mechanism 36. The elevator mechanism 36 may be configured to reach wafer cassettes 22 placed on cassette storage positions 24 at different vertical heights within the cassette handling space 12.

In an embodiment, the elevator mechanism 36 of the first cassette handler 26 may be arranged on or adjacent a second wall 38 and the elevator mechanism 36 of the second cassette handler 28 may be arranged on or adjacent a third wall 40. The second and the third wall 38, 40 may bound the cassette handling space 12 on opposite ends.

When the elevator mechanisms 36 of the first cassette handler 26 and the second cassette handler 28 are arranged on or adjacent opposite ends of the cassette handling space 12, the cassette handlers 26, 28 themselves are also arranged on or adjacent opposite ends of the cassette handling space 12. The first and second set 30, 32 of cassette storage positions will then also be arranged on or adjacent opposite ends of the cassette handling space 12. The first set 30 of cassette storage positions 24 may be arranged on or adjacent the second wall 38, while the second set 32 of cassette storage positions 24 may be arranged on or adjacent the third wall 40. The first set 30 of cassette storage positions 24 will cover roughly half of the cassette handling space 12, nearest the first end, while the second set 32 of cassette storage positions 24 will cover roughly another half the cassette handling space, nearest the second end. Because both the first cassette handler 26 and the second cassette handler 28 only need to cover roughly half of the area with respect to a known cassette handler, the reach of each may be much smaller. A smaller reach means that a less complicated and robust cassette handler 26, 28 may be feasible which is beneficial in view of a manufacturing costs.

In an embodiment, the cassette storage may be configured to store 10 to 50 wafer cassettes 22. The cassette storage may e.g., be configured to store at least 30 wafer cassettes 22. The cassette storage may also be configured to store at least 40 wafer cassettes 22. This means that the cassette storage has at least 40 cassette storage positons 24. Typically about 50 to 250 wafers are needed to fill a wafer boat 58. Typically there are about 25 wafers provided in a wafer cassette 22. This means that typically 2 to 10 wafer cassettes 22 are needed to fill one wafer boat 58. By having at least 40 cassette storage positions 24, enough wafer cassettes 22 may be stored to fill at least two wafer boats 58, in particular approximately four wafer boats. Thus the loading and unloading of wafer cassettes 22 to and from the cassette handling space 12 can be postponed for quite some time while the vertical batch furnace assembly 10 is processing the wafers from the wafer cassettes 22 which are stored in the cassette handling space 12.

In an embodiment, the wafer cassettes 22 may be embodied as Front Opening Unified Pods (FOUP's). FOUP's are standardized wafer cassettes for wafers in the industry. Using FOUP's is advantageous for exchangeability of the wafer cassettes 22 between the vertical batch furnace assembly 10 and other wafer processing machines.

In an embodiment, the vertical batch furnace assembly 10 may further comprise at least one cassette in-out port 42, 44 provided in a wall 16, 38, 40, 46 bounding the cassette handling space 12. This may be the already mentioned first, second or third walls 16, 38, 40, but it may also be a distinct fourth wall 46. The cassette handling mechanism 26, 28 may be configured to additionally transfer wafer cassettes 22 to and from the at least one cassette in-out port 42, 44. The at least one cassette in-out port 42, 44 may provide the entrance to and the exit from the vertical batch furnace assembly 10, for the exchange of wafer cassettes 22 between the vertical batch furnace assembly 10 and the outside world, in particular the clean room environment.

The at least one cassette in-out port 42, 44 may comprise a first and a second cassette in-out port 42, 44 in the fourth wall 46 which may bound the cassette handling space 12 at an end opposite the first wall 16. The first cassette in-out port 42 may be reachable by the first cassette handler 26. The second cassette in-out port 44 may be reachable by the second cassette handler 28.

By associating both the first and second cassette in-out ports 42, 44 with respectively the first and second cassette handlers 26, 28, and thus with the first and second sets 30, 32 of cassette storage positions 24, a clear separation is made within the cassette handling space 12. Each of the cassette handlers 26, 28 may have its own in-out port 42, 44 and cassette storage positions 24. This means they can operate independently of each other, without needing to wait for each other or get in each others way. This may improve the efficiency of the handling of the wafer cassettes 22 within the cassette handling space 12.

In an embodiment, the vertical batch furnace assembly 10 may comprise storage racks 48, illustrated in FIG. 3 , which have at least a part of the cassette storage positions 24. The storage racks 48 may have all of the cassette storage positions 24. The cassette handling space 12 may be accessible via a closeable maintenance opening via which at least one storage rack 48 is removable from the cassette handling space 12.

A storage rack 48 is basically a rack of shelves on which wafer cassettes 22 may be placed. It is a basic design without moving parts. By arranging the wafer cassettes 22 on the storage racks 48 enough cassette storage positions 24 may be created. When such a storage rack 48 is removable from the cassette handling space 12, it may simply be removed by e.g. a hand truck, when such a removal would be necessary or desired. One or more storage rack(s) 48 could for example be removed to give service personnel easy access to e.g., the first wall 16 at which a cassette door opener device 54 may need maintenance. The cassette handler arm 34 of the second cassette handler 28 may for example be moved in an upper position by means of the elevator mechanism 36 so that the service personnel may pass under the cassette handler arm 34. For example by removing three storage racks 48 from the area that holds the second set 32 of the cassette storage positions 24, easy access to the cassette door opener device 54 may be obtained.

In an embodiment, the vertical batch furnace assembly 10 may be provided with a substantially rectangular footprint having two opposite short sides defining a width 50 of the vertical batch furnace assembly 10 and having two opposite long sides defining a length 52 of the vertical batch furnace assembly 10. The width 50 of the vertical batch furnace assembly 10 may be 2.2 meter or less or preferably 1.7 meter or less. The length 52 of the vertical batch furnace assembly 10 may be 5 meter or less, preferably 4 meter or less.

By having a substantial rectangular footprint, multiple vertical batch furnace assemblies 10 may be arranged adjacent to each other, thus making optimal use of available floor area. Adjacent vertical batch furnace assemblies 10 with rectangular footprints may have no unused space in between them. A width 50 of less than 2.2 meter is beneficial in view of interchangeability with other vertical batch furnace assemblies, for example from other manufacturers/brands. A length 52 of 5 meter or less, preferably 4 meter or less, is beneficial for reducing the footprint altogether.

In an embodiment, the vertical batch furnace assembly 10 may comprise a cassette door opener device 54. The cassette door opener device 54 may be placed at or near the wafer transfer position 20. The cassette door opener device 54 may be arranged on the first wall 16. The cassette door opener device 54 may be configured to open a cassette door of a wafer cassette 22 which is placed in the wafer transfer position 20. The cassette door opener device 54 may thus automatically open a cassette door of a wafer cassette 22 which is placed in the wafer transfer position 20.

In an embodiment, the vertical batch furnace assembly 10 may further comprise a wafer handler 56, a process chamber 60, and a wafer boat handling device positioned under the process chamber 60. The wafer handler 56 may be positioned in the wafer handling space 14 and may be configured to transfer wafers between a wafer cassette 22 in the wafer transfer position 20 and a wafer boat 58. The process chamber 60 may be configured to process wafers accommodated in the wafer boat 58. The wafer boat handling device may be positioned adjacent the wafer handling space 14. The wafer boat handling device may be provided with the wafer boat 58 in a wafer boat transfer position, and may be configured to transport the wafer 58 boat to the process chamber 60, and to the wafer boat transfer position.

When the wafer boat 58 is in the wafer boat transfer position, the wafer hander 56 may transfer unprocessed wafers from a wafer cassette 22 in the wafer transfer position 20 to the wafer boat 58, and transfer processed wafers from the wafer boat 58 to the wafer cassette 22 in the wafer transfer position 20. When the wafer boat 58 is loaded with one or more wafers, the wafer boat handling device may transport the loaded wafer boat 58 to the process chamber 60. In the process chamber 60 the wafers may be processed. After processing, the wafer boat handling device may transport the processed wafer boat 58 from the process chamber 60 back to the wafer boat transfer position, in which position the wafer hander 56 may transfer the processed wafer or wafers from the wafer boat 58 to a wafer cassette 22 in the wafer transfer position 20 and transfer unprocessed wafers from the wafer cassette 22 in the wafer transfer position 20 to the wafer boat 58, thus completing a batch process of the vertical batch furnace assembly 10.

In an embodiment, the first set 30 and the second set 32 of the cassette storage positions 24 may be different. This means that the first set 30 and the second set 32 of the cassette storage positions 24 are not equal sets and do not overlap. The first set 30 and the second set 32 may be disjoint sets. Alternatively, they may also be overlapping sets. The advantage of disjoint sets is that each cassette storage positon 24 is associated with only one cassette handler 26, 28. This will minimize the interference between the two cassette handlers 26, 28 which may increase the efficiency and reliability of the cassette handlers 26, 28, and may lessen the chance of break downs.

In an embodiment, the cassette storage may be provided with a rotatable cassette storage carousel having at least a part of the cassette storage positions 24. The cassette storage carousel may comprise a central vertical support which is rotatable around a vertical carousel axis. The cassette storage carousel 18 may also comprise a number of platform stages connected to the central vertical support and having the cassette storage positions 24. The cassette storage carousel may further comprise a drive assembly which may be operatively connected to the central vertical support for rotating the central vertical support with the number of platform stages around the vertical carousel axis. Such a cassette storage carousel is an effective way to store wafer cassettes 22 in a limited space. Because the platform stages are rotatable, the cassette storage carousel may rotate unused or unoccupied cassette storage positions 24 in the general direction of an associated cassette handler 26, 28. The cassette handler 26, 28 may thus always place a wafer cassette on the nearest cassette storage position 24. The cassette handlers 26, 28 thus can suffice with a smaller reach than would be needed if the cassette handler 26, 28 were to reach all cassette storage positions 24 by itself.

Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this description are not necessarily all referring to the same embodiment.

Furthermore, it is noted that particular features, structures, or characteristics of one or more of the various embodiments which are described above may be used implemented independently from one another and may be combined in any suitable manner to form new, not explicitly described embodiments. The reference numbers used in the detailed description and the claims do not limit the description of the embodiments nor do they limit the claims. The reference numbers are solely used to clarify.

LEGEND

-   -   10—vertical batch furnace assembly     -   12—cassette handling space     -   14—wafer handling space     -   16—first wall     -   18—wafer transfer opening     -   20—wafer transfer position     -   22—wafer cassette     -   24—cassette storage position     -   26—first cassette handler     -   28—second cassette handler     -   30—first set (of cassette storage position)     -   32—second set (of cassette storage position)     -   34—cassette handler arm     -   36—elevator mechanism     -   38—second wall     -   40—third wall     -   42—first cassette in-out port     -   44—second cassette in-out port     -   46—fourth wall     -   48—storage rack     -   50—width     -   52—length     -   54—cassette door opener device     -   56—wafer handler     -   58—wafer boat     -   60—process chamber 

The invention claimed is:
 1. A vertical batch furnace assembly for processing wafers comprising: a cassette handling space; a wafer handling space; a first wall separating the cassette handling space from the wafer handling space and having at least one wafer transfer opening in front of which, at a side of the first wall which is directed to the cassette handling space, a wafer transfer position for a wafer cassette is provided; wherein the cassette handling space comprises: a cassette storage having a plurality of cassette storage positions and configured to store a plurality of wafer cassettes provided with a plurality of wafers; and a cassette handling mechanism comprising a first cassette handler configured to transfer wafer cassettes between a first set of the cassette storage positions and the wafer transfer position, wherein the cassette handling mechanism is provided with a second cassette handler configured to transfer wafer cassettes between a second set of the cassette storage positions and the wafer transfer position, wherein the first cassette handler and the second cassette handler operate independently, and wherein the cassette handling space is accessible via a closeable maintenance opening via which at least one storage rack is removable from the cassette handling space.
 2. The vertical batch furnace assembly according to claim 1, wherein the first and the second cassette handler are each provided with a cassette handler arm, and an elevator mechanism configured to reach wafer cassettes placed on cassette storage positions at different vertical heights within the cassette handling space, wherein each cassette handler arm and an elevator mechanism are independently operational.
 3. The vertical batch furnace assembly according to claim 2, wherein the elevator mechanism of the first cassette handler is arranged on or adjacent a second wall and the elevator mechanism of the second cassette handler is arranged on or adjacent a third wall, wherein the second and the third wall bound the cassette handling space on opposite ends.
 4. The vertical batch furnace assembly according to claim 1, wherein the cassette storage is configured to store at least 30 wafer cassettes.
 5. The vertical batch furnace assembly according to claim 1, wherein the cassette storage is configured to store at least 40 wafer cassettes.
 6. The vertical batch furnace assembly according to claim 1, wherein the wafer cassettes are embodied as Front Opening Unified Pods (FOUP's).
 7. The vertical batch furnace assembly according to claim 1, further comprising at least one cassette in-out port provided in a wall bounding the cassette handling space, wherein the cassette handling mechanism is configured to additionally transfer wafer cassettes to and from the at least one cassette in-out port.
 8. The vertical batch furnace assembly according to claim 7, wherein the at least one cassette in-out port comprises a first and a second cassette in-out port in a fourth wall which bounds the cassette handling space at an end opposite the first wall, wherein the first cassette in-out port is reachable by the first cassette handler and wherein the second cassette in-out port is reachable by the second cassette handler.
 9. The vertical batch furnace assembly according to claim 1, comprising storage racks which include at least a part of the cassette storage positions.
 10. The vertical batch furnace assembly according to claim 1, provided with a substantially rectangular footprint having two opposite short sides defining a width of the vertical batch furnace assembly and having two opposite long sides defining a length of the vertical batch furnace assembly, wherein the width of the vertical batch furnace assembly is 2.2 meter or less.
 11. The vertical batch furnace assembly according to claim 10, wherein the width of the vertical batch furnace assembly is 1.7 meter or less.
 12. The vertical batch furnace assembly according to claim 10, wherein the length of the vertical batch furnace assembly is 5 meter or less, or 4 meter or less.
 13. The vertical batch furnace assembly according to claim 1, wherein for each wafer transfer opening the vertical batch furnace assembly comprises: a cassette door opener device configured to open a cassette door of a wafer cassette which is placed in the wafer transfer position.
 14. The vertical batch furnace assembly according to claim 1, wherein the vertical batch furnace assembly further comprises: a wafer handler positioned in the wafer handling space and configured to transfer wafers between a wafer cassette in the wafer transfer position and a wafer boat; a process chamber configured to process wafers accommodated in the wafer boat; and a wafer boat handling device positioned under the process chamber and adjacent the wafer handling space, wherein the wafer boat handling device is provided with the wafer boat in a wafer boat transfer position, and is configured to transport the wafer boat to the process chamber, and to the wafer boat transfer position.
 15. The vertical batch furnace assembly according claim 1, wherein the first set and second set of the cassette storage positions are different.
 16. The vertical batch furnace assembly according to claim 1, wherein the cassette storage is provided with a rotatable cassette storage carrousel having at least a part of the cassette storage positions. 